SAN DIEGO -- Customs officials said Sunday that the heightened border security will last indefinitely.

The United States has sharply intensified inspections and anti-terrorist surveillance along the Mexico and Canada borders since the Sept. 11 attacks.

BORDER TRAFFIC Check delays at the Calif.-Mexico border Check San Diego traffic

More inspectors on more overtime are asking more questions at the 150 border crossing sites. They are opening more trunks and peering at cars more often with imaging equipment.

In addition, more agents are taking to the air to patrol the vast stretches of desert, forest and waters along the 6,000 miles of border shared by the United States with its two neighbors.

Waits up to 15 hours have been reported at border crossings. Most travelers are accepting heavier security with patience and patriotism, but some border towns feel pangs from their pocketbooks. Some Americans favor even more inspectors and stricter screening to snag terrorists before they strike.

The strengthened border watch has snared some people, but not the most wanted, suspected terrorists. Bolstering their security at U.S. request, Mexican authorities rounded up a large group of migrants from the Middle East without proper papers. Dozens of Iraqi Christians who planned to seek asylum in San Diego were being held by Mexican officials.

Within one hour of the suicide air-hijacking attacks in New York City and Washington, authorities went on their highest alert at the Mexico and Canada borders. Some small border stations that have been closing at night were staffed around the clock.

At busy crossings into El Paso, Texas, some agents carried assault rifles and wore bulletproof vests.

Merchants were worried in border towns that rely on shoppers and workers from across the border. In Douglas, Arizona, Mayor Ray Borane said there has been a "drastic drop" in business.